Increasingly, it is necessary to justify the expense of providing additional effectiveness by comparing the value for the cost of alternative interventions (e.g. using cost-effectiveness analysis). While the statistical methodology for assessing, interpreting, and defending evidence of effectiveness is well developed, the methodology for the evaluation of costs is less so. The objective of this study is to advance the methods of evaluating costs as part of cost-effectiveness analysis and apply the new methods to clinical studies of alcohol treatments. The aims of this proposal focus on addressing problem areas that potentially undermine the policy relevance and interpretability of economic evidence derived from clinical trials. These problem areas are: (1) Resource costing; (2) Estimating incremental costs of treatment; (3) Accommodating attrition in cost data; (4) Estimating sample size and power for cost-effectiveness; and (5) Generalizing cost and outcome information. Our approach will be to develop advancements in these areas, demonstrate our new methods using an NIAAA funded clinical trial, validate using simulation, and then disseminate. By developing the methodology of cost analysis we aim to improve the policy relevance and interpretability of economic evidence in trial based data.